Chapter 110: Wulin's Secret Art of Forcing Sound into Lines
What is the key to launching a satellite?
It's tracking.
Low-orbit satellites enter and leave the country quickly, circling the earth in one or two hours, and passing overhead with a "whoosh". The low-orbit reconnaissance satellites that Lao Zhao and his team sent to the future are only 300 kilometers high and circle the earth in one hour. Such a high running speed will make Banxia face the same problem - this little thing runs too fast to be tracked, and if it is difficult to track, it is difficult to aim, and it is impossible to aim the antenna at it, so it is difficult to receive data.
"How do you usually track the satellite's orbit when you launch a satellite?" Bai Yang asked.
"Use software, such as SatOrbit and Heavens-Above. They are free and can check the orbital parameters of all public satellites. You can know exactly when they appear and when they pass overhead, and at what angle and direction." Wang Ning moved a small stool to sit in the living room, using pliers to straighten a clothes hanger. "There is also a more professional one, STK. Similar software is everywhere, so that satellites around the world no longer have privacy for you."
Obviously, these softwares would not have existed in BG4MSR's era, as humans were completely extinct, there was no Internet, no servers, and no one was maintaining or updating them.
"She definitely can't find the satellite orbit over there by herself. How can she find it? We just need to tell her." Bai Zhen also moved a small stool to sit in the living room, holding a pair of pliers in his hand to cut the clothes hanger. "If we are lucky and the satellite re-enters the orbit without deviation, then once we report the parameters, she will be able to align quickly."
"In fact, the best plan is to bring a relay satellite and place it in a synchronous orbit at an altitude of 36,000 kilometers." Zhao Bowen also brought a small stool and sat in the living room. He also held a pair of pliers in his hand and cut and straightened a clothes hanger. "In this way, the relay satellite will always be suspended above the girl's head. The reconnaissance satellite will transmit data to the relay satellite, and the relay satellite will transmit the data back to the ground. We don't have to spend energy tracking it. Otherwise, if we stand on the roof of the building with a Yagi antenna all day long to follow the satellite, we will develop spinal disease."
"Then you should ask them to bring a relay satellite."
Bai Zhen cut the clothes hanger in his hand with a "click".
"I mentioned it a long time ago, but was scolded by the space crew." Zhao Bowen curled his lips, "They asked me, are you still a human being? You are not a human being!"
"What's the result? The relay satellite belt was not brought?"
Wang Ning also cut the clothes hanger in his hand with a "click".
"I brought it, but they warned me that it would greatly increase the difficulty of orbit design and the probability of failure of the satellite's re-entry into orbit." Zhao Bowen replied, "I said there's nothing we can do about it. Can you imagine a little girl standing on the rooftop holding a Yagi antenna and spinning around all day? She doesn't have to do anything else?"
The three old men sat together and chattered, but they did not stop working, just like the women in the village sitting together to gossip and knit sweaters, and a lot of gossip was spread that way, except that Bai Zhen, Wang Ning, and Zhao Bowen did not have knitting needles and wool in their hands, but pliers and clothes hangers, and the "clicking" sounds came one after another.
When Bai Yang got home from school in the afternoon, he saw them sitting together and abusing a clothes hanger. They cut the clothes hanger into pieces. The scene was horrific. He didn't know what deep hatred they had.
What is this doing?
This is making a Yagi antenna.
The Yagi antenna is undoubtedly the most commonly used antenna type in the HAM community. Compared with ordinary rod antennas and dipole antennas, the advantages of the Yagi antenna are high gain and high directivity. The signal is polarized in one direction. In layman's terms, other antennas are big light bulbs with scattered light, while the Yagi antenna is a flashlight that only emits light in one direction.
Due to the polarization characteristics of the Yagi antenna signal, it is also the antenna that HAMs often use to reach satellites. Since the power of ordinary amateur radio stations is very low, and the power of satellites is even lower, the communication between the radio station and the satellite is like a dumb person talking to a deaf person, and the two people are thousands of miles apart - usually it is impossible for them to hear each other, unless the dumb person masters the martial arts skills to force the sound into a line.
This line that forces sound into a line is the Yagi antenna.
Bai Zhen put down the clothes rack in his hand and picked up a thin wooden board from the floor. It was unknown which furniture factory it was picked up from, but it was about one meter long.
"What is the uplink and downlink frequency of that relay satellite?"
"The uplink frequency is 144MHZ and the downlink frequency is 430MHZ." Zhao Bowen replied.
"The transmission speed of U-band is a bit slow, it would be better if you could develop an X-band," said Wang Ning.
"It's complicated to do X-band reception. The reconnaissance satellite and the relay satellite are connected by X-band. The relay satellite can store the data and slowly transmit it back to Earth. There's no need to rush." Zhao Bowen picked up the tape measure from the coffee table. "How long should the reflector be?"
"The upward wave is two meters long, and the reflector is one meter long, which is half the wavelength."
Bai Zhen took the measuring tape and measured a length of one meter on the clothes drying rack that was pulled straight up. "No, this clothes drying rack is not big enough. It can't measure one meter. Is there a bigger clothes drying rack?"
My mother came out of the kitchen and said, "You have ruined all the clothes drying racks in our house."
"I'll ask Xiao Zhu to buy a large size."
Wang Ning said this and dialed the phone.
That night, Xiao Zhu ran around all the supermarkets in Qinhuai District.
The clothes hanger when straightened becomes metal wire. Bai Zhen cut off a one-meter-long piece of metal wire and used it as a reflector for the Yagi antenna. The structure of the Yagi antenna is so simple that it can be made with wooden strips and a clothes hanger. This is why Bai Zhen and others chose Yagi. It can be made from materials found anywhere, is easy to make, and is extremely friendly to novices.
The wooden strip is used as the central axis, and five straightened clothes drying racks are vertically inserted on the wooden strip in sequence. It looks like fish bones and forms a "丰" shape, which is a simple five-element Yagi antenna.
The rearmost and longest clothesline is called a reflector, and it focuses the signal, like the mercury bowl in a flashlight.
The second to last clothesline is called a vibrator. The vibrator is the core of all antennas. It is the signal source. The electric current bounces wildly on the vibrator to generate electromagnetic waves.
The remaining three clothes hangers are called directors. They guide the radiation direction of the radio waves, making it radiate in the direction of the antenna, so as to achieve the purpose of hitting wherever it is pointed.
"Will you teach her how to do it after you're done?" Bai Yang sat aside and watched the three people doing handicrafts. Rubbing the Yagi antenna by hand is the basic skill of old HAM. Zhao Bowen has almost forgotten it, but his father and Lao Wang's skills are still fresh.
"Once we've confirmed that this thing works, we'll have her copy it over there and make an identical one," Daddy replied. "Just make do with what you have."
"This is easy and you can learn it in no time," Zhao Bowen said. "With the Yagi antenna, she can receive the signal from the satellite and then pass it to us. Everything goes smoothly."
"How long should the vibrator be?"
"96 centimeters, or 97 centimeters, it's up to you to cut it."
"There are three left that are the same length."
"Both are 88 centimeters."
"Pay attention to the spacing. Do we want one with higher gain or better bandwidth characteristics?"
"Just give them a try. After they're done, give them a try with AO-91 to see how it works... Also, make sure to adjust the impedance."
"50 euros for closing your eyes."
"Who of you brought the SWR instrument?"
"It's okay, I'll let Xiao Zhu bring one over!"
The trio finally completed a UV double-stage Yagi. When they lifted it up and pointed it eastward, it felt like they were carrying a machine gun - Banxia also thought so. Two days later, when she finished the Yagi, she felt that when she wielded it, it was just like the Fang Tian Hua Ji used by Lu Bu in Ma Zhong.
(End of this chapter)
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